blob: 4faa7a5fa7c773d45d08e6adf4c763b7d97eba66 [file] [log] [blame]
.. default-domain:: cpp
.. highlight:: sh
.. _chapter-pw-bloat:
--------
pw_bloat
--------
The bloat module provides tools to generate size report cards for output
binaries using `Bloaty McBloatface <https://github.com/google/bloaty>`_ and
Pigweed's GN build system.
Bloat report cards allow tracking the memory usage of a system over time as code
changes are made and provide a breakdown of which parts of the code have the
largest size impact.
.. _bloat-howto:
Defining size reports
=====================
Size reports are defined using the GN template ``pw_size_report``. The template
requires at least two executable targets on which to perform a size diff. The
base for the size diff can be specified either globally through the top-level
``base`` argument, or individually per-binary within the ``binaries`` list.
**Arguments**
* ``title``: Title for the report card.
* ``base``: Optional default base target for all listed binaries.
* ``binaries``: List of binaries to size diff. Each binary specifies a target,
a label for the diff, and optionally a base target that overrides the default
base.
* ``source_filter``: Optional regex to filter labels in the diff output.
* ``full_report``: Boolean flag indicating whether to output a full report of
all symbols in the binary, or a summary of the segment size changes. Default
false.
.. code::
import("$dir_pw_bloat/bloat.gni")
executable("empty_base") {
sources = [ "empty_main.cc" ]
}
exectuable("hello_world_printf") {
sources = [ "hello_printf.cc" ]
}
exectuable("hello_world_iostream") {
sources = [ "hello_iostream.cc" ]
}
pw_size_report("my_size_report") {
title = "Hello world program using printf vs. iostream"
base = ":empty_base"
binaries = [
{
target = ":hello_world_printf"
label = "Hello world using printf"
},
{
target = ":hello_world_iostream"
label = "Hello world using iostream"
},
]
}
When the size report target runs, it will print its report card to stdout.
Additionally, size report targets also generate ReST output, which is described
below.
Documentation integration
=========================
Bloat reports are easy to add to documentation files. All ``pw_size_report``
targets output a file containing a tabular report card. This file can be
imported directly into a ReST documentation file using the ``include``
directive.
For example, the ``simple_bloat_loop`` and ``simple_bloat_function`` size
reports under ``//pw_bloat/examples`` are imported into this file as follows:
.. code:: rst
Simple bloat loop example
^^^^^^^^^^^^^^^^^^^^^^^^^
.. include:: examples/simple_bloat_loop
Simple bloat function example
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.. include:: examples/simple_bloat_function
Resulting in this output:
Simple bloat loop example
^^^^^^^^^^^^^^^^^^^^^^^^^
.. include:: examples/simple_bloat_loop
Simple bloat function example
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.. include:: examples/simple_bloat_function